Implementations of the claimed invention generally may relate to schemes for enhancing video information and, more particularly, to such schemes that alter the sharpness of the video information.
Video information may be transmitted via a medium in time and/or space for viewing at a separate time and/or location. In some cases, the medium may be a transmission medium, such as carrier waves (e.g., terrestrial and/or cable-carried) or protocol-based data networks. In some cases, the medium may be a storage medium (e.g., tape, hard disk, digital video disc (DVD), etc.) that may store the video information prior to its display. Typically, the video data may be encoded into one of a number of formats before transmission. Some encoding formats may include, but are not limited to, MPEG-1, MPEG-2, MPEG-4, Advanced Video Coding (AVC) (e.g., MPEG-4, part 10 and ITU-T Recommendation H.264), Windows Media Video 9 (WMV-9), and/or SMPTE's VC-1.
Such encoding of video information may remove (e.g., by quantizing, etc.) some higher-frequency content in the original video information. The decoded information may appear smoothed and/or somewhat fuzzy when displayed. This phenomenon may not be unique to encoded video data, but may also be present in, for example, transmitted analog video due to impediments in the transmission path. Thus, it may be desirable to increase the sharpness of received and/or decoded video data to improve its perceived picture quality.
To further introduce the concept of sharpening video, a one-dimensional example will be discussed with regard to FIGS. 1A and 1B. An image in a video sequence may include, for example, luma and chroma signals (e.g., Y, U, and V) sampled in both the horizontal and vertical directions. When the image is roughly uniform in a certain area, the sample values may be substantially the same. When an edge (e.g. a horizontal edge) exists in the image, however, the sample values in the horizontal direction may undergo an abrupt change in value. FIG. 1A illustrates a one-dimensional plot 110 of luma values that change somewhat abruptly over a number of pixels.
To sharpen the video signal, overshoots/undershoots may be generated in the signal (e.g., Y, U or V) by adding the second derivative (e.g., d2Y/dx2) of plot 110 to itself. FIG. 1B illustrates a plot 120 that has been so sharpened by the addition of undershoot 130 and overshoot 140. Adding overshoot/undershoot 140/130 may boost perceived, higher frequency components. Because plot 120 may have steeper edges than plot 110, its transition may be perceived as visually sharper than that of unsharpened plot 110.
Some schemes for increasing the sharpness of video information, however, may also increase noise within the video information to unacceptable levels.